1. Ergebnisse der Mathematik und ihrer Grenzgebiete, (N.F.), Heft 22;Hahn, Wolfgang,1959
2. Controllability of linear dynamical systems;Kalman, R. E.;Contributions to Differential Equations,1963
3. Mathematics in Science and Engineering, Vol. 4;LaSalle, Joseph,1961
4. The time optimal control problem;LaSalle, J. P.,1960